Prevention of peroxynitrite-dependent tyrosine nitration and inactivation of alpha1-antiproteinase by antibiotics

iNOS expressing macrophages co-localize with nitrotyrosine staining after myocardial infarction in humans

Introduction

Inducible nitric oxide synthase (iNOS) produces micromolar amounts of nitric oxide (NO) upon the right stimuli, whose further reactions can lead to oxidative stress. In murine models of myocardial infarction (MI), iNOS is known to be expressed in infiltrating macrophages, which at early onset enter the infarcted zone and are associated with inflammation. In contrast cardiac tissue resident macrophages are thought to enhance regeneration of tissue injury and re-establish homeostasis. Both detrimental and beneficial effects of iNOS have been described, still the role of iNOS in MI is not fully understood. Our aim was to examine cell expression patterns of iNOS and nitrotyrosine (NT) production in human MI.

Material and Methods

We examined in postmortem human MI hearts the iNOS mRNA expression by means of qPCR. Further we performed immunohistochemical stainings for cell type identification. Afterwards a distance analysis between iNOS and NT was carried out to determine causality between iNOS and NT production.

Results

iNOS mRNA expression was significantly increased in infarcted regions of human MI hearts and iNOS protein expression was detected in resident macrophages in infarcted human hearts as well as in controls hearts, being higher in resident macrophages in MI hearts compared to control. Furthermore in MI and in healthy human hearts cells showing signs of NT production peaked within 10–15 µm proximity of iNOS+ cells.

Discussion

These results indicate that, unexpectedly, resident macrophages are the main source of iNOS expression in postmortem human MI hearts. The peak of NT positive cells within 10–15 µm of iNOS+ cells suggest an iNOS dependent level of NT and therefore iNOS dependent oxidative stress. Our results contribute to understanding the role of iNOS in human MI.

Sepsis-Associated Encephalopathy: A Mini-Review of Inflammation in the Brain and Body

Sepsis is defined as a life-threatening multi-organ dysfunction triggered by an uncontrolled host response to infectious disease. Systemic inflammation elicited by sepsis can cause acute cerebral dysfunction, characterized by delirium, coma, and cognitive dysfunction, known as septic encephalopathy. Recent evidence has reported the underlying mechanisms of sepsis. However, the reasons for the development of inflammation and degeneration in some brain regions and the persistence of neuroinflammation remain unclear. This mini-review describes the pathophysiology of region-specific inflammation after sepsis-associated encephalopathy (SAE), clinical features, and future prospects for SAE treatment. The hippocampus is highly susceptible to inflammation, and studies that perform treatments with antibodies to cytokine receptors, such as interleukin-1β, are in progress. Future development of clinically applicable therapies is expected.

Doxycycline, an Antibiotic or an Anti-Inflammatory Agent? The Most Common Uses in Dermatology

Doxycycline is a synthetic tetracycline that was approved in 1967. This wide-spectrum antibiotic has been shown to also have useful anti-inflammatory properties that make it suitable for the treatment of a number of noninfectious conditions. Tetracyclines are probably the most commonly prescribed antibiotics in dermatology, where they are usually used at doses lower than those effective against infections. They also have an excellent efficacy and safety profile. Because of doxycycline's ability to inhibit the molecular pathways associated with certain processes, this antibiotic can be used to treat hair follicle diseases, granulomatous diseases, and vascular proliferation, among other conditions. The main properties of doxycycline and its many applications in dermatology make this drug one that specialists should become familiar with.

Amelioration of elastase-induced lung emphysema and reversal of pulmonary hypertension by pharmacological iNOS inhibition in mice

BACKGROUND AND PURPOSE

Chronic obstructive pulmonary disease, encompassing chronic airway obstruction and lung emphysema, is a major worldwide health problem and a severe socio-economic burden. Evidence previously provided by our group has shown that inhibition of inducible NOS (iNOS) prevents development of mild emphysema in a mouse model of chronic tobacco smoke exposure and can even trigger lung regeneration. Moreover, we could demonstrate that pulmonary hypertension is not only abolished in cigarette smoke-exposed iNOS^-/- mice but also precedes emphysema development. Possible regenerative effects of pharmacological iNOS inhibition in more severe models of emphysema not dependent on tobacco smoke, however, are hitherto unknown.

EXPERIMENTAL APPROACH

We have established a mouse model using a single dose of porcine pancreatic elastase or saline, intratracheally instilled in C57BL/6J mice. Emphysema, as well as pulmonary hypertension development was determined by both structural and functional measurements.

KEY RESULTS

Our data revealed that (i) emphysema is fully established after 21 days, with the same degree of emphysema after 21 and 28 days post instillation, (ii) emphysema is stable for at least 12 weeks and (iii) pulmonary hypertension is evident, in contrast to smoke models, only after emphysema development. Oral treatment with the iNOS inhibitor N(6)-(1-iminoethyl)-l-lysine (L-NIL) was started after emphysema establishment and continued for 12 weeks. This resulted in significant lung regeneration, evident in the improvement of emphysema and reversal of pulmonary hypertension.

CONCLUSION AND IMPLICATIONS

Our data indicate that iNOS is a potential new therapeutic target to treat severe emphysema and associated pulmonary hypertension.

LINKED ARTICLES

This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Demonstration by Infra-Red Imaging of a Temperature Control Defect in a Decompression Sickness Model Testing Minocycline

The prevention, prognosis and resolution of decompression sickness (DCS) are not satisfactory. The etiology of DCS has highlighted thrombotic and inflammatory phenomena that could cause severe neurological disorders or even death. Given the immunomodulatory effects described for minocycline, an antibiotic in widespread use, we have decided to explore its effects in an experimental model for decompression sickness. 40 control mice (Ctrl) and 40 mice treated orally with 90 mg/kg of minocycline (MINO) were subjected to a protocol in a hyperbaric chamber, compressed with air. The purpose was to mimic a scuba dive to a depth of 90 msw and its pathogenic decompression phase. Clinical examinations and blood counts were conducted after the return to the surface. For the first time they were completed by a simple infrared (IR) imaging technique in order to assess feasibility and its clinical advantage in differentiating the sick mice (DCS) from the healthy mice (NoDCS). In this tudy, exposure to the hyperbaric protocol provoked a reduction in the number of circulating leukocytes. DCS in mice, manifesting itself by paralysis or convulsion for example, is also associated with a fall in platelets count. Cold areas ( < 25°C) were detected by IR in the hind paws and tail with significant differences (p < 0.05) between DCS and NoDCS. Severe hypothermia was also shown in the DCS mice. The ROC analysis of the thermograms has made it possible to determine that an average tail temperature below 27.5°C allows us to consider the animals to be suffering from DCS (OR = 8; AUC = 0.754, p = 0.0018). Minocycline modulates blood analysis and it seems to limit the mobilization of monocytes and granulocytes after the provocative dive. While a higher proportion of mice treated with minocycline experienced DCS symptoms, there is no significant difference. The infrared imaging has made it possible to show severe hypothermia. It suggests an modification of thermregulation in DCS animals. Surveillance by infrared camera is fast and it can aid the prognosis in the case of decompression sickness in mice.

Opioids, gliosis and central immunomodulation

Neuropathic pain is a common health problem that affects millions of people worldwide. Despite being studied extensively, the cellular and molecular events underlying the central immunomodulation and the pathophysiology of neuropathic pain is still controversial. The idea that 'glial cells are merely housekeepers' is incorrect and with respect to initiation and maintenance of neuropathic pain, microglia and astrocytes have important roles to play. Glial cells differentially express opioid receptors and are thought to be functionally modulated by the activation of these receptors. In this review, we discuss evidence for glia-opioid modulation of pain by focusing on the pattern of astrocyte and microglial activation throughout the progress of nerve injury/neuropathic pain. Activation of astrocytes and microglia is a key step in central immunomodulation in terms of releasing pro-inflammatory markers and propagation of a 'central immune response'. Inhibition of astrocytes before and after induction of neuropathic pain has been found to prevent and reverse neuropathic pain, respectively. Moreover, microglial inhibitors have been found to prevent (but not to reverse) neuropathic pain. As they are expressed by glia, opioid receptors are expected to have a role to play in neuropathic pain.

Doxycycline as an anti-inflammatory agent: updates in dermatology

Doxycycline, a tetracycline antibiotic, is widely used in the field of dermatology for its antibiotic properties, anti-inflammatory properties and good safety profile. Over the past decades, numerous studies have clarified some of the anti-inflammatory mechanisms of doxycycline. In this review article, we aimed to provide an update on recent data on the anti-inflammatory properties of doxycycline and its potential role in cutaneous inflammatory diseases. Better understanding of these mechanisms might offer the practicing clinicians a better use of this therapeutic tool. In addition, research in this field could help clarify pathogenic aspects of inflammatory dermatologic diseases responsive to this medication. Further research is needed to fully elucidate the potential of doxycycline as an anti-inflammatory agent, and the development of new topical vehicles could open ways to new therapeutic possibilities for dermatologists.

Minocycline affects human neutrophil respiratory burst and transendothelial migration

OBJECTIVE

This study aimed at investigating the in vitro activity of minocycline and doxycycline on human polymorphonuclear (h-PMN) cell function.

METHODS

h-PMNs were isolated from whole venous blood of healthy subjects; PMN oxidative burst was measured by monitoring ROS-induced oxidation of luminol and transendothelial migration was studied by measuring PMN migration through a monolayer of human umbilical vein endothelial cells. Differences between multiple groups were determined by ANOVA followed by Tukey's multiple comparison test; Student's t test for unpaired data for two groups.

RESULTS

Minocycline (1-300 µM) concentration dependently and significantly inhibited oxidative burst of h-PMNs stimulated with 100 nM fMLP. Ten micromolar concentrations, which are superimposable to C _max following a standard oral dose of minocycline, promoted a 29.8 ± 4 % inhibition of respiratory burst (P < 0.001; n = 6). Doxycycline inhibited ROS production with a lesser extent and at higher concentrations. 10-100 µM minocycline impaired PMN transendothelial migration, with maximal effect at 100 µM (42.5 ± 7 %, inhibition, n = 5, P < 0.001).

CONCLUSIONS

These results added new insight into anti-inflammatory effects of minocycline exerted on innate immune h-PMN cell function.

A 30-years review on pharmacokinetics of antibiotics: is the right time for pharmacogenetics?

Drug bioavailability may vary greatly amongst individuals, affecting both efficacy and toxicity: in humans, genetic variations account for a relevant proportion of such variability. In the last decade the use of pharmacogenetics in clinical practice, as a tool to individualize treatment, has shown a different degree of diffusion in various clinical fields.

In the field of infectious diseases, several studies identified a great number of associations between host genetic polymor-phisms and responses to antiretroviral therapy. For example, in patients treated with abacavir the screening for HLA-B*5701 before starting treatment is routine clinical practice and standard of care for all patients; efavirenz plasma levels are influenced by single nucleotide polymorphism (SNP) CYP2B6-516G> T (rs3745274). Regarding antibiotics, many studies investigated drug transporters involved in antibiotic bioavailability, especially for fluoroquinolones, cephalosporins, and antituberculars. To date, few data are available about pharmacogenetics of recently developed antibiotics such as tigecycline, daptomycin or linezolid. Considering the effect of SNPs in gene coding for proteins involved in antibiotics bioavailability, few data have been published.

Increasing knowledge in the field of antibiotic pharmacogenetics could be useful to explain the high drug inter-patients variability and to individualize therapy. In this paper we reported an overview of pharmacokinetics, pharmacodynamics, and pharmacogenetics of antibiotics to underline the importance of an integrated approach in choosing the right dosage in clinical practice.

Minocycline protects against oxidative damage and alters energy metabolism parameters in the brain of rats subjected to chronic mild stress

Studies have been suggested that minocycline can be a potential new agent for the treatment of depression. In addition, both oxidative stress and energy metabolism present an important role in pathophysiology of depression. So, the present study was aimed to evaluate the effects of minocycline on stress oxidative parameters and energy metabolism in the brain of adult rats submitted to the chronic mild stress protocol (CMS). After CMS Wistar, both stressed animals as controls received twice ICV injection of minocycline (160 μg) or vehicle. The oxidative stress and energy metabolism parameters were assessed in the prefrontal cortex (PF), hippocampus (HIP), amygdala (AMY) and nucleus accumbens (Nac). Our findings showed that stress induced an increase on protein carbonyl in the PF, AMY and NAc, and mynocicline injection reversed this alteration. The TBARS was increased by stress in the PF, HIP and NAc, however, minocycline reversed the alteration in the PF and HIP. The Complex I was incrased in AMY by stress, and minocycline reversed this effect, however reduced Complex I activity in the NAc; Complex II reduced in PF and AMY by stress or minocycline; the Complex II-III increased in the HIP in stress plus minocycline treatment and in the NAc with minocycline; in the PF and HIP there were a reduced in Complex IV with stress and minocycline. The creatine kinase was reduced in AMY and NAc with stress and minocycline. In conclusion, minocycline presented neuroprotector effects by reducing oxidative damage and regulating energy metabolism in specific brain areas.

The role of microglia activation in the development of sepsis-induced long-term cognitive impairment

Oxidative stress and inflammation is likely to be a major step in the development of sepsis-associated encephalopathy (SAE) and long-term cognitive impairment. To date, it is not known whether brain inflammation and oxidative damage are a direct consequence of systemic inflammation or whether these events are driven by brain resident cells, such as microglia. Therefore, the aim of this study is to evaluate the effect of minocycline on behavioral and neuroinflammatory parameters in rats submitted to sepsis. Male Wistar rats were subjected to sepsis by cecal ligation and puncture (CLP). The animals were divided into sham-operated (Sham+control), sham-operated plus minocycline (sham+MIN), CLP (CLP+control) and CLP plus minocycline (CLP+MIN) (100 μg/kg, administered as a single intracerebroventricular (ICV) injection). Some animals were killed 24h after surgery to assess the breakdown of the blood brain barrier, cytokine levels, oxidative damage to lipids (TBARS) and proteins in the hippocampus. Some animals were allowed to recover for 10 days when step-down inhibitory avoidance and open-field tasks were performed. Treatment with minocycline prevented an increase in markers of oxidative damage and inflammation in the hippocampus after sepsis. This was associated with an improvement in long-term cognitive performance. In conclusion, we demonstrated that the inhibition of the microglia by an ICV injection of minocycline was able to decrease acute brain oxidative damage and inflammation as well as long-term cognitive impairment in sepsis survivors.

Minocycline: far beyond an antibiotic

Minocycline is a second-generation, semi-synthetic tetracycline that has been in therapeutic use for over 30 years because of its antibiotic properties against both gram-positive and gram-negative bacteria. It is mainly used in the treatment of acne vulgaris and some sexually transmitted diseases. Recently, it has been reported that tetracyclines can exert a variety of biological actions that are independent of their anti-microbial activity, including anti-inflammatory and anti-apoptotic activities, and inhibition of proteolysis, angiogenesis and tumour metastasis. These findings specifically concern to minocycline as it has recently been found to have multiple non-antibiotic biological effects that are beneficial in experimental models of various diseases with an inflammatory basis, including dermatitis, periodontitis, atherosclerosis and autoimmune disorders such as rheumatoid arthritis and inflammatory bowel disease. Of note, minocycline has also emerged as the most effective tetracycline derivative at providing neuroprotection. This effect has been confirmed in experimental models of ischaemia, traumatic brain injury and neuropathic pain, and of several neurodegenerative conditions including Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, Alzheimer's disease, multiple sclerosis and spinal cord injury. Moreover, other pre-clinical studies have shown its ability to inhibit malignant cell growth and activation and replication of human immunodeficiency virus, and to prevent bone resorption. Considering the above-mentioned findings, this review will cover the most important topics in the pharmacology of minocycline to date, supporting its evaluation as a new therapeutic approach for many of the diseases described herein.

Non-antibiotic properties of tetracyclines and their clinical application in dermatology

Dermatologists have used tetracyclines since the 1950s to treat disorders that do not necessarily have an infectious aetiology. Their anti-inflammatory and anti-collagenase properties contribute significantly to their success in treating diseases such as rosacea and acne. This article reviews the non-antibiotic properties of tetracyclines and their clinical application in dermatology.

What is behind the non-antibiotic properties of minocycline?

Minocycline is a second-generation, semi-synthetic tetracycline that has been in use in therapy for over 30 years for its antibiotic properties against both Gram-positive and Gram-negative bacteria. It displays antibiotic activity due to its ability to bind to the 30S ribosomal subunit of bacteria and thus inhibit protein synthesis. More recently, it has been described to exert a variety of biological actions beyond its antimicrobial activity, including anti-inflammatory and anti-apoptotic activities, inhibition of proteolysis, as well as suppression of angiogenesis and tumor metastasis, which have been confirmed in different experimental models of non-infectious diseases. There are also many studies that have focused on the mechanisms involved in these non-antibiotic properties of minocycline, including anti-oxidant activity, inhibition of several enzyme activities, inhibition of apoptosis and regulation of immune cell activation and proliferation. This review summarizes the current findings in this topic, mainly focusing on the mechanisms underlying the immunomodulatory and anti-inflammatory activities of minocycline.

Nitrative stress in inflammatory lung diseases

Since the discovery of nitric oxide (NO), an intracellular signal transmitter, the role of NO has been investigated in various organs. In the respiratory system, NO derived from the constitutive type of NO synthase (cNOS, NOS1, NOS3) induces bronchodilation and pulmonary vasodilatation to maintain homeostasis. In contrast, the roles of excessive NO derived from the inducible type of NOS (iNOS, NOS2) in airway and lung inflammation in inflammatory lung diseases including bronchial asthma and chronic obstructive pulmonary disease (COPD) are controversial. In these inflammatory lung diseases, excessive nitrosative stress has also been observed. In asthma, some reports have shown that nitrosative stress causes airway inflammation, airway hyperresponsiveness, and airway remodeling, which are the features of asthma, whereas others have demonstrated the anti-inflammatory role of NO derived from NOS2. In the case of refractory asthma, more nitrosative stress has been reported to be observed in such airways compared with that in well-controlled asthmatics. In COPD, reactive nitrogen species (RNS), which are NO and NO-related molecules including nitrogen dioxide and peroxynitrite, cause lung inflammation, oxidative stress, activation of matrix metalloproteinase, and inactivation of antiprotease, which are involved in the pathophysiology of the disease. In the present paper, we review the physiological and pathophysiological effects of NO and NO-related molecules in the respiratory system and in inflammatory lung diseases.

Doxycycline protects against pilocarpine-induced convulsions in rats, through its antioxidant effect and modulation of brain amino acids

This work evaluated doxycycline (2nd generation tetracycline) protection against pilocarpine-induced convulsions in rats. The animals were treated with doxycycline (Dox: 10 to100 mg/kg, i.p., 7days), 30min before the pilocarpine injection (P: 300mg/kg, i.p.) and observed for cholinergic signs, latencies to the first convulsion and death. Amino acid concentrations, lipid peroxidation and nitrite levels in temporal cortices were determined as well as the radical scavenging activity. Doxycycline increased latencies to the first convulsion and death as compared to the untreated P300 group. It also decreased glutamate and aspartate, increased GABA, blocked nitrite formation, reduced TBARS contents and showed a radical scavenging activity. Finally, doxycycline decreased the number of degenerating neurons (evaluated by fluoro-jade staining) and increased the number of viable neurons (assessed by cresyl violet staining) as compared do the P300 group. The antioxidant effect associated with decreased levels of excitatory and increased levels of inhibitory amino acids could explain the neuroprotective effect of doxycycline.

Neuroprotection by minocycline caused by direct and specific scavenging of peroxynitrite

Minocycline prevents oxidative protein modifications and damage in disease models associated with inflammatory glial activation and oxidative stress. Although the drug has been assumed to act by preventing the up-regulation of proinflammatory enzymes, we probed here its direct chemical interaction with reactive oxygen species. The antibiotic did not react with superoxide or (•)NO radicals, but peroxynitrite (PON) was scavenged in the range of ∼1 μm minocycline and below. The interaction of pharmacologically relevant minocycline concentrations with PON was corroborated in several assay systems and significantly exceeded the efficacy of other antibiotics. Minocycline was degraded during the reaction with PON, and the resultant products lacked antioxidant properties. The antioxidant activity of minocycline extended to cellular systems, because it prevented neuronal mitochondrial DNA damage and glutathione depletion. Maintenance of neuronal viability under PON stress was shown to be solely dependent on direct chemical scavenging by minocycline. We chose α-synuclein (ASYN), known from Parkinsonian pathology as a biologically relevant target in chemical and cellular nitration reactions. Submicromolar concentrations of minocycline prevented tyrosine nitration of ASYN by PON. Mass spectrometric analysis revealed that minocycline impeded nitrations more effectively than methionine oxidations and dimerizations of ASYN, which are secondary reactions under PON stress. Thus, PON scavenging at low concentrations is a novel feature of minocycline and may help to explain its pharmacological activity.

Hepatocyte-protective and anti-oxidant effects of rifampicin on human chronic hepatitis C and murine acute hepatocyte disorder

Rifampicin (RFP) is a semisynthetic antibiotic derived from the rifamycins and is one of the most commonly used pharmaceutical compounds worldwide in the treatment of tuberculosis. We previously reported that low-dose and long-term oral administration of RFP to 6 hepatitis C virus-related liver cirrhosis patients who were at high risk for presenting with hepatocellular carcinoma (HCC) resulted in a marked suppression of the occurrence of HCC without showing an adverse effect. The underlying mechanism was found to be due to the anticancer effect based on the potent anti-angiogenic properties of RFP. The present study revealed that RFP has an additional hepatocyte-protective effect by lowering the release of hepatic enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in chronic hepatitis C patients. Experimentally, we were able to show that RFP had hepatocyte-protective effects in acute hepatocyte disorder models of mice and rats induced by concanavalin A and by D-galactosamine, respectively: RFP significantly prevented an increase in the levels of ALT, AST and lactate dehydrogenase in these animal models. In addition, we found that RFP had a strong anti-oxidant action which was approximately three times stronger than the action of silibinin, an anti-inflammatory agent of human hepatic stellate cells, implicating that the hepatocyte-protective effects of RFP are mediated by its anti-oxidant activity. These results reveal that oral administration of RFP exerts not only a prophylactic effect on the occurrence or recurrence of HCC for an extensive period of time, but also exerts hepatocyte-protective effects on both human chronic hepatitis C and acute hepatocyte disorder in rodent models, and the anti-oxidant activity of RFP is implicated to participate in the latter effects.

Mechanisms of minocycline-induced suppression of simian immunodeficiency virus encephalitis: inhibition of apoptosis signal-regulating kinase 1

Human immunodeficiency virus (HIV) infection of the central nervous system (CNS) can lead to cognitive dysfunction, even in individuals treated with highly active antiretroviral therapy. Using an established simian immunodeficiency virus (SIV)/macaque model of HIV CNS disease, we previously reported that infection shifts the balance of activation of mitogen-activated protein kinase (MAPK) signaling pathways in the brain, resulting in increased activation of the neurodegenerative MAPKs p38 and JNK. Minocycline treatment of SIV-infected macaques reduced the incidence and severity of SIV encephalitis in this model, and suppressed the activation of p38 in the brain. The purpose of this study was to further examine the effects of minocycline on neurodegenerative MAPK signaling. We first demonstrated that minocycline also decreases JNK activation in the brain and levels of the inflammatory mediator nitric oxide (NO). We next used NO to activate these MAPK pathways in vitro, and demonstrated that minocycline suppresses p38 and c-Jun N-terminal kinase (JNK) activation by reducing intracellular levels, and hence, activation of apoptosis signal-regulating kinase 1 (ASK1), a MAPK kinase capable of selectively activating both pathways. We then demonstrated that ASK1 activation in the brain during SIV infection is suppressed by minocycline. By suppressing p38 and JNK activation pathways, which are important for the production of and responses to inflammatory mediators, minocycline may interrupt the vicious cycle of inflammation that both results from, and promotes, virus replication in SIV and HIV CNS disease.

TNF signaling inhibition in the CNS: implications for normal brain function and neurodegenerative disease

The role of tumor necrosis factor (TNF) as an immune mediator has long been appreciated but its function in the brain is still unclear. TNF receptor 1 (TNFR1) is expressed in most cell types, and can be activated by binding of either soluble TNF (solTNF) or transmembrane TNF (tmTNF), with a preference for solTNF; whereas TNFR2 is expressed primarily by microglia and endothelial cells and is preferentially activated by tmTNF. Elevation of solTNF is a hallmark of acute and chronic neuroinflammation as well as a number of neurodegenerative conditions including ischemic stroke, Alzheimer's (AD), Parkinson's (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). The presence of this potent inflammatory factor at sites of injury implicates it as a mediator of neuronal damage and disease pathogenesis, making TNF an attractive target for therapeutic development to treat acute and chronic neurodegenerative conditions. However, new and old observations from animal models and clinical trials reviewed here suggest solTNF and tmTNF exert different functions under normal and pathological conditions in the CNS. A potential role for TNF in synaptic scaling and hippocampal neurogenesis demonstrated by recent studies suggest additional in-depth mechanistic studies are warranted to delineate the distinct functions of the two TNF ligands in different parts of the brain prior to large-scale development of anti-TNF therapies in the CNS. If inactivation of TNF-dependent inflammation in the brain is warranted by additional pre-clinical studies, selective targeting of TNFR1-mediated signaling while sparing TNFR2 activation may lessen adverse effects of anti-TNF therapies in the CNS.

Amyotrophic lateral sclerosis: from current developments in the laboratory to clinical implications

Amyotrophic lateral sclerosis (ALS) is a late-onset progressive degeneration of motor neurons occurring both as a sporadic and a familial disease. The etiology of ALS remains unknown, but one fifth of instances are due to specific gene defects, the best characterized of which is point mutations in the gene coding for Cu/Zn superoxide dismutase (SOD1). Because sporadic and familial ALS affect the same neurons with similar pathology, it is hoped that understanding these gene defects will help in devising therapies effective in both forms. A wealth of evidence has been collected in rodents made transgenic for mutant SOD1, which represent the best available models for familial ALS. Mutant SOD1 likely induces selective vulnerability of motor neurons through a combination of several mechanisms, including protein misfolding, mitochondrial dysfunction, oxidative damage, cytoskeletal abnormalities and defective axonal transport, excitotoxicity, inadequate growth factor signaling, and inflammation. Damage within motor neurons is enhanced by noxious signals originating from nonneuronal neighboring cells, where mutant SOD1 induces an inflammatory response that accelerates disease progression. The clinical implication of these findings is that promising therapeutic approaches can be derived from multidrug treatments aimed at the simultaneous interception of damage in both motor neurons and nonmotor neuronal cells.

Inhibition of matrix metalloproteinases prevents peroxynitrite-induced contractile dysfunction in the isolated cardiac myocyte

BACKGROUND AND PURPOSE

The potent oxidant peroxynitrite (ONOO(-)) induces mechanical dysfunction in the intact heart in part through activation of matrix metalloproteinase-2 (MMP-2). This effect may be independent of the proteolytic actions of MMPs on extracellular matrix proteins. The purpose of this study was to examine the effects of ONOO(-) on contractile function at the level of the single cardiac myocyte and whether this includes the action of MMPs.

EXPERIMENTAL APPROACH

Freshly isolated ventricular myocytes from adult rats were superfused with Krebs-Henseleit buffer at 21 degrees C and paced at 0.5 Hz. Contractility was measured using a video edge-detector. ONOO(-) or decomposed ONOO(-) (vehicle control) were co-infused over 40 min to evaluate the contraction cease time (CCT). The effects of ONOO(-) on intracellular [Ca(2+)] were determined in myocytes loaded with calcium green-1 AM. MMP-2 activity was measured by gelatin zymography.

KEY RESULTS

ONOO(-) (30-600 microM) caused a concentration-dependent reduction in CCT. Myocytes subjected to 300 microM ONOO(-) had a shorter CCT than decomposed ONOO(-) (14.9+1.5 vs 32.2+3.5 min, n=7-8; P<0.05) and showed increased MMP-2 activity. The MMP inhibitors doxycycline (100 microM) or PD 166793 (2 microM) reduced the decline in CCT induced by 300 microM ONOO(-). ONOO(-) caused shorter calcium transient cease time and significant alterations in intracellular [Ca(2+)] homoeostasis which were partially prevented by doxycycline.

CONCLUSIONS AND IMPLICATIONS

This is the first demonstration that inhibition of MMPs protects the cardiac myocyte from ONOO(-)-induced contractile failure via an action unrelated to proteolysis of extracellular matrix proteins.

Protective effect of minocycline, a semi-synthetic second-generation tetracycline against 3-nitropropionic acid (3-NP)-induced neurotoxicity

3-Nitropropionic acid (3-NP) is an irreversible inhibitor of the electron transport enzyme succinate dehydrogenase, a mitochondrial Complex II enzyme. Minocycline is a semi-synthetic second-generation tetracycline with neuroprotective activity and has the capability to effectively cross the blood-brain barrier. We investigated the effects of minocycline on behavioral, biochemical, inflammation related and neurochemical alterations induced by the sub-chronic administration of 3-nitropropionic acid to rats. Chronic pre-administration of minocycline (50 and 100mg/kg) dose dependently prevented 3-NP-induced dysfunction behavioral (hypoactivity, memory retention, locomotor and rota-rod activity). In addition, 3-NP produced a marked increase in lipid peroxidation levels whereas decreased the activities of catalase and succinate dehydrogenase. In contrast, pretreatment of 3-NP injected rats with minocycline resulted in the attenuation of all these alterations. A marked increase in an inflammatory cytokine TNF-alpha by 3-NP was also decreased by minocycline treatment. Neurochemically, the administration of 3-NP significantly decreased the levels of catecholamines in the brain homogenates (dopamine, norepinephrine and serotonin) which were reversed by pretreatment of minocycline. The present finding explains the neuroprotective effect of minocycline against 3-NP toxicity by virtue of its antioxidant and anti-inflammatory activity.

Minocycline and riluzole brain disposition: interactions with p-glycoprotein at the blood-brain barrier

Amyotrophic lateral sclerosis is a neurodegenerative fatal disease. The only drug recognized to increase the survival time is riluzole(RLZ). In animal models, minocycline (MNC) delayed the onset of the disease and increased the survival time (in combination with RLZ). The objective of our work was to study the interactions between RLZ, MNC and the efflux pump p-glycoprotein (p-gp) at the blood-brain barrier. We investigated these two drugs as: (i) p-gp substrates by comparing their brain uptake in CF1 mdr1a (-/-) and mdr1a (+/+) mice, (ii) p-gp modulators by studying their effect on the cerebral uptake of digoxin. mdr1a (-/-) mice showed higher brain uptake of MNC and RLZ than mdr1a (+/+) (in a 1.6- and 1.4-fold, respectively); and in mdr1a (+/+) mice pre-treated with repeated doses of MNC, brain uptake of digoxin was increased. When both drugs were administrated to mdr1a (+/+) mice, MNC increased the brain uptake of RLZ in a 2.1-fold. In conclusion, MNC and RLZ are both p-gp substrates. MNC is also a p-gp inhibitor and increases the brain diffusion of RLZ. In vitro experiments with the GPNT cell line confirmed these results. These interactions should be taken into account in the design of future clinical trials.

Innate immunity in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative condition in which motor neurons are selectively targeted. Although the underlying cause remains unclear, evidence suggests a role for innate immunity in disease pathogenesis. Neuroinflammation in areas of motor neuron loss is evident in presymptomatic mouse models of ALS and in human patients. Efforts aimed at attenuating the inflammatory response in ALS animal models have delayed symptom onset and extended survival. Seemingly conversely, attempts to sensitize cells of the innate immune system and modulate their phenotype have also shown efficacy. Effectors of innate immunity in the CNS appear to have ambivalent potential to promote either repair or injury. Because ALS is a syndromic disease in which glutamate excitotoxicity, altered cytoskeletal protein metabolism, oxidative injury, mitochondrial dysfunction and neuroinflammation all contribute to motor neuron degeneration, targeting inflammation via modulation of microglial function therefore holds significant potential as one aspect of therapeutic intervention and could provide insight into the exclusive vulnerability of motor neurons.

Chronic Inflammation, Immune Response, and Infection in Abdominal Aortic Aneurysms

Abdominal aortic aneurysms (AAA) are associated with atherosclerosis, transmural degenerative processes, neovascularization, decrease in content of vascular smooth muscle cells, and a chronic infiltration, mainly located in the outer aortic wall. The chronic infiltration consists mainly of macrophages, lymphocytes, and plasma cells. The dominant cells are Th2 restricted CD3+ lymphocytes expressing interleukine 4, 5, 8, and 10, and tumor necrosis factor-alpha for regulation of the local immune response. They also produce interferon-gamma and CD40 ligand to stimulate surrounding cells to produce matrix metalloproteases and cysteine proteases for aortic matrix remodeling. The lymphocyte activation may be mediated by microorganisms as well as autoantigens generated from vascular structural proteins, perhaps through molecular mimicry. As in autoimmune diseases, the risk of AAA is increased by certain genotypes concerning human leucocyte antigen class II. These types are also associated with increased aneurysmal inflammation indicating a genetic susceptibility to aortic inflammation. Chlamydia pneumoniae is often detected in AAA but the validity of the methods can be questioned, and two small antibiotic trials have been disappointing. However, serum antibodies against C. pneumoniae have been associated with AAA growth and cross-react with AAA wall proteins. Thus, immune responses mediated by microorganisms and autoantigens may play a pivotal role in AAA pathogenesis.

Rifampicin attenuates the MPTP-induced neurotoxicity in mouse brain

Rifampicin, an antibacterial drug, is highly effective in the treatment of tuberculosis and leprosy. Recently, it has been reported to have neuroprotective effects in in vitro and in vivo models. This study was designed to elucidate its neuroprotective effects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity (known as an in vivo mouse model of Parkinson's disease). Mice were injected intraperitoneally (i.p.) with MPTP (10 mg/kg) four times at 1-h intervals, and brains were analyzed 3 or 7 days later. Rifampicin at 20 mg/kg (i.p., twice) had protective effects against MPTP-induced neuronal damage (immunohistochemical changes in tyrosine hydroxylase) in both the substantia nigra and striatum. Rifampicin also protected against the MPTP-induced depletions of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in the striatum. The maximal concentrations of rifampicin between 30 and 240 min after a single rifampicin injection (20 mg/kg, i.p.) were 2.6 microM (at 30 min) in plasma and 0.77 microM (at 60 min) in striatum. Next, the effects of rifampicin on oxidative stress [lipid peroxidation in mouse brain homogenates and free radical-scavenging activity against diphenyl-p-picrylhydrazyl (DPPH)] were evaluated to clarify the underlying mechanism. At 1 microM or more, rifampicin significantly inhibited both lipid peroxidation in the striatum and free radical production. These findings suggest that in mice, rifampicin can reach brain tissues at concentrations sufficient to attenuate MPTP-induced neurodegeneration in the nigrostriatal dopaminergic neuronal pathway, and that an inhibitory effect against oxidative stress may be partly responsible for its observed neuroprotective effects.

Involvement of reactive nitrogen oxides for acquisition of metastatic properties of benign tumors in a model of inflammation-based tumor progression

The cells of a weakly tumorigenic and non-metastatic murine fibrosarcoma (QR-32) are converted into highly malignant tumors (acquiring metastatic potential) once they have grown in vivo after being co-implanted with gelatin sponge which induces inflammation. In the present study, we examined whether nitric oxide (NO) is involved in the inflammation-based tumor progression by administrating a specific inhibitor to inducible nitric oxide synthase, aminoguanidine (AG). First, we co-implanted 1 x 10(5) QR-32 cells with gelatin sponge (10 x 5 x 3 mm piece) into a subcutaneous space in C57BL6 mice. Administration of AG in drinking water (1%) had started 2 days before the tumor implantation and continued until the termination of the experiment. The incidence of tumor formation and the tumor growth did not differ between AG-treated group and -untreated group. On day 28, we excised the arising tumors to establish culture cell lines for evaluation of their acquisition of metastatic phenotype in other normal mice. Metastasis incidence and the number of metastatic colonies were significantly reduced in the tumor cell lines obtained from AG-treated mice compared to those from non-treated mice (p < 0.05). Immunohistochemical analysis demonstrated that inducible nitric oxide synthase and nitrotyrosine in the inflamed lesion were reduced in the AG-administered mice. However, intensity of 8-hydroxy-2-deoxyguanosine was not different between the groups. These results showed that nitric oxide and its reactive nitrogen oxide species cooperatively play a pivotal role in the progression of benign tumor cells in inflamed lesions.

Interaction of rifalazil with oxidant-generating systems of human polymorphonuclear neutrophils

It is well acknowledged that ansamycins display immunosuppressive and anti-inflammatory properties in vitro and in vivo. Rifalazil, a new ansamycin derivative, has not been studied in the context of inflammation. In particular, there are no data on the possible interference of rifalazil with oxidant production by phagocytes. We have compared the antioxidant properties of rifalazil to those of rifampin, a drug well known in this context, by using cellular and acellular oxidant-generating systems. Oxidant production by polymorphonuclear neutrophils was measured in terms of cytochrome c reduction, lucigenin-amplified chemiluminescence (Lu-ACL), and the 2',7'-dichlorofluorescin diacetate H2 (DCFDA-H2) technique (intracellular oxidant production). Rifalazil impaired O2- production in a concentration-dependent manner, with 50% inhibitory concentrations (IC50) (concentrations which inhibit 50% of the response) of 5.4 (30 and 60 min of incubation) and 6.4 (30 min) mg/liter, respectively, for phorbol myristate acetate (PMA) and formyl-methionyl-leucyl-phenylalanine (fMLP) stimulation. In agreement with the published fMLP-like activity of rifampin, the inhibitory effect of rifampin was significantly greater for fMLP (IC50 of 5.6 mg/liter) than for PMA (IC50 of 58 mg/liter) stimulation. Alteration of intracellular oxidant production was also observed with IC50 values similar to those obtained by the cytochrome assay. In addition, rifalazil and rifampin (> or = 25 mg/liter) scavenged O2-, as demonstrated by the acellular (hypoxanthine-xanthine oxidase) system. Interference with light detection systems was evidenced for both drugs by Lu-ACL. The clinical relevance of the antioxidant effect of rifalazil demonstrated in vitro, in particular its potential anti-inflammatory activity, requires further investigation.

Neuroprotective effects of minocycline against in vitro and in vivo retinal ganglion cell damage

The purpose of this study was to determine whether minocycline, a semi-synthetic tetracycline derivative, reduces (a) the in vitro neuronal damage occurring after serum deprivation in cultured retinal ganglion cells (RGC-5, a rat ganglion cell line transformed using E1A virus) and/or (b) the in vivo retinal damage induced by N-methyl-D-aspartate (NMDA) intravitreal injection in mice. In addition, we examined minocycline's putative mechanisms of action against oxidative stress and endoplasmic reticulum (ER) stress. In vitro, retinal damage was induced by 24-h serum deprivation, and cell viability was measured by Hoechst 33342 staining or resazurin reduction assay. In cultures of RGC-5 cells maintained in serum-free medium for up to 24 h, the number of cells undergoing cell death was reduced by minocycline (0.2-20 microM). Serum deprivation resulted in increased oxidative stress, as revealed by an increase in the fluorescence intensity for 5-(and-6)-chloromethyl-2', 7'-dichlorodihydrofluorescein diacetate (CM-H2DCFDA), a reactive oxygen species (ROS) indicator. Minocycline at 2 and 20 microM inhibited this ROS production. However, even at 20 microM minocycline did not inhibit the retinal damage induced by tunicamycin (an ER stress inducer). Furthermore, in mice in vivo minocycline at 90 mg/kg intraperitoneally administered 60 min before an NMDA intravitreal injection reduced the NMDA-induced retinal damage. These findings indicate that minocycline has neuroprotective effects against in vitro and in vivo retinal damage, and that an inhibitory effect on ROS production may contribute to the underlying mechanisms.

Lack of evidence of direct mitochondrial involvement in the neuroprotective effect of minocycline

Minocycline has been reported to exert neuroprotection through inhibition of inflammatory processes and of mitochondrial cell death pathway. To further characterize the neuroprotective effect of minocycline, we determined its efficacy in different neuronal damage paradigms involving inflammation or mitochondrial dysfunction. In transient global ischaemia in gerbils, minocycline reduced hippocampal neuronal damage measured by peripheral type benzodiazepine binding sites density, a marker of microglial activation. The antiinflammatory properties of minocycline were confirmed on the model of carrageenan-induced paw oedema in rats. The use of two experimental animal models involving administration of mitochondrial toxins inhibiting a different complex of the mitochondrial respiratory chain permitted the exploration of the mitochondrial impact of minocycline. Although minocycline exhibited a marked efficacy in 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP; complex I inhibitor)-induced neurotoxicity in mice, it was ineffective in malonate (complex II inhibitor)-induced striatal lesion in rats. In vitro investigations on energized mitochondria isolated from rat liver showed that minocycline (1 microM) did not inhibit the swelling induced by MPP+(1-methyl-4-phenylpyridinium). Moreover, higher concentrations of minocycline induced swelling. From these experiments, the neuroprotective activity of minocycline appears more related to its antiinflammatory activity than to a direct beneficial action on mitochondria.

Minocycline inhibits oxidative stress and decreases in vitro and in vivo ischemic neuronal damage

The neuroprotective effects of minocycline-which is broadly protective in neurologic-disease models featuring cell death and is being evaluated in clinical trials-were investigated both in vitro and in vivo. For the in vivo study, focal cerebral ischemia was induced by permanent middle cerebral artery occlusion in mice. Minocycline at 90 mg/kg intraperitoneally administered 60 min before or 30 min after (but not 4 h after) the occlusion reduced infarction, brain swelling, and neurologic deficits at 24 h after the occlusion. For the in vitro studies, we used cortical-neuron cultures from rat fetuses in which neurotoxicity was induced by 24-h exposure to 500 microM glutamate. Furthermore, the effects of minocycline on oxidative stress [such as lipid peroxidation in mouse forebrain homogenates and free radical-scavenging activity against diphenyl-p-picrylhydrazyl (DPPH)] were evaluated to clarify the underlying mechanism. Minocycline significantly inhibited glutamate-induced cell death at 2 microM and lipid peroxidation and free radical scavenging at 0.2 and 2 microM, respectively. These findings indicate that minocycline has neuroprotective effects in vivo against permanent focal cerebral ischemia and in vitro against glutamate-induced cell death and that an inhibition of oxidative stress by minocycline may be partly responsible for these effects.

Central Proinflammatory Cytokines and Pain Enhancement

Enhanced pain is a component of the 'sickness response' which is an evolutionarily adaptive constellation of responses that enhance the survival of the host. Proinflammatory cytokines mediate these sickness behaviors, and whether proinflammatory cytokines are involved in exaggerated pain has become an intriguing question. Studies suggest that spinal cord glial cells (astrocytes and microglia) are activated in conditions that lead to enhanced pain. Not only is glial activation associated with enhanced pain, but it is also integral to the induction and maintenance of these pain states. Proinflammatory cytokines can be released by activated astrocytes and microglia within the central nervous system. This review will discuss the role of proinflammatory cytokines in experimental models of prolonged pain states. Administration of exogenous proinflammatory cytokines facilitates pain, and agents that antagonize proinflammatory cytokine actions have been shown to block and/or reverse enhanced pain. These findings suggest that blocking the synthesis and/or release of proinflammatory cytokines may be viable strategies for the treatment of pathological pain. Gene therapy to augment the endogenous anti-inflammatory cytokine, interleukin-10, is one of the more promising therapies currently under study.

The basic aspects of therapeutics in amyotrophic lateral sclerosis

Once thought to be a single pathological disease state, amyotrophic lateral sclerosis (ALS) is now recognized to be the limited phenotypic expression of a complex, heterogeneous group of biological processes, resulting in an unrelenting loss of motor neurons. On average, individuals affected with the disease live <5 years. In this article, the complex nature of the pathogenesis of ALS, including features of age dependency, environmental associations, and genetics, is reviewed. Once held to be uncommon, it is now clear that ALS is associated with a frontotemporal dementia and that this process may reflect disturbances in the microtubule-associated tau protein metabolism. The motor neuron ultimately succumbs in a state where significant disruptions in neurofilament metabolism, mitochondrial function, and management of oxidative stress exist. The microenvironment of the neuron becomes a complex milieu in which high levels of glutamate provide a source of chronic excitatory neurotoxicity, and the contributions of activated microglial cells lead to further cascades of motor neuron death, perhaps serving to propagate the disease once established. The final process of motor neuron death encompasses many features of apoptosis, but it is clear that this alone cannot account for all features of motor neuron loss and that aspects of a necrosis-apoptosis continuum are at play. Designing pharmacological strategies to mitigate against this process thus becomes an increasingly complex issue, which is reviewed in this article.

Minocycline Slows Disease Progression in a Mouse Model of Amyotrophic Lateral Sclerosis

There is currently no effective pharmacological treatment for amyotrophic lateral sclerosis (ALS). Because recent evidence suggests that secondary inflammation and caspase activation may contribute to neurodegeneration in ALS, we tested the effects of minocycline, a second-generation tetracycline with anti-inflammatory properties, in mice expressing a mutant superoxide dismutase (SOD1(G37R)) linked to human ALS. Administration of minocycline into the diet, beginning at late presymptomatic stage (7 or 9 months of age), delayed the onset of motor neuron degeneration, muscle strength decline, and it increased the longevity of SOD1(G37R) mice by approximately 5 weeks for approximately 70% of tested mice. Moreover, less activation of microglia was detected at early symptomatic stage (46 weeks) and at the end stage of disease in the spinal cord of SOD1(G37R) mice treated with minocycline. These results indicate that minocycline, which is clinically well tolerated, may represent a novel and effective drug for treatment of ALS.

Tetracycline derivatives and ceftriaxone, a cephalosporin antibiotic, protect neurons against apoptosis induced by ionizing radiation

DNA damage induced by low doses of ionizing radiation causes apoptosis, which is partially mediated via the generation of free radicals. Both free radicals and apoptosis are involved in the majority of brain diseases, including stroke, Alzheimer's disease and amyotrophic lateral sclerosis. Because previous studies have shown that tetracycline derivatives doxycycline and minocycline have anti-inflammatory effects and are protective against brain ischemia, we studied whether minocycline and doxycycline or ceftriaxone, a cephalosporin antibiotic with the potential to inhibit excitotoxicity, protect neurons against ionizing radiation in primary cortical cultures. A single dose of 1 Gy significantly increased lactate dehydrogenase release, induced DNA fragmentation in neurons and triggered microglial proliferation. Treatment with minocycline (20 nM), doxycycline (20 nM) and ceftriaxone (1 microM) significantly reduced irradiation-induced lactate dehydrogenase release and DNA fragmentation. The most efficient protection was achieved by minocycline treatment, which also inhibited the irradiation-induced increase in microglial cell number. Our results suggest that some tetracycline derivatives, such as doxycycline and minocycline, and ceftriaxone, a cephalosporin derivative, protect neurons against apoptotic death.

Indicators of infection with Chlamydia pneumoniae are associated with expansion of abdominal aortic aneurysms

PURPOSE

Chlamydia Pneumoniae has been shown to be associated with atherosclerosis, myocardial infarction, and abdominal aortic aneurysms (AAAs). The possible association between AAA expansion and C pneumoniae infection was therefore assessed.

METHODS

Blood samples were taken from patients with an AAA that was considered for surgical repair after having been diagnosed by means of the Chichester aneurysm screening program (UK) as having an initially infrarenal aortic diameter of 3.0 to 5.9 cm. The patients were examined prospectively for as long as 11.5 years (mean, 4.1 years) with ultrasound scanning. Of 110 patients considered for surgery, 90 men and 10 women had blood samples taken. Their IgG and IgA antibodies against C pneumoniae were measured by means of a microimmunofluorescence test. Unpaired t tests, multiple linear regression analyses, and logistic regression analyses were used for statistical analysis.

RESULTS

A total of 44% (95% CI, 31%-55%) of the men with an AAA had an IgA titer of 64 or more, an IgG titer of 128 or more, or both, compared with 10% of the women with an AAA (OR = 7.2; 95% CI, 1.05-160.8). A titer of IgG of 128 or more was significantly associated with higher expansion (5.3 vs 2.6 mm per year), even after adjustment for initial AAA size and age. A significant positive correlation between both IgA and IgG titers and mean annual expansion was observed (r = 0.28; 95% CI, 0.05-0.49; and r = 0.45; 95% CI, 0.24-0.62, respectively), persisting after adjusting for initial AAA size and age. An IgG titer of 128 or more was present significantly more often in cases with an expansion greater than 1 cm annually (adjusted OR = 12.6; 95% CI, 1.37-293).

CONCLUSION

A high proportion of men with an AAA has signs of infection with C pneumoniae. The progression of their AAAs was positively correlated with the presence of indicators of C pneumoniae infection.

Reactive oxygen species: a potential role in the pathogenesis of periodontal diseases

The pathological events leading to the destruction of the periodontium during inflammatory periodontal diseases are likely to represent complex interactions involving an imbalance in enzymic and non-enzymic degradative mechanisms. This paper aims to review the increasing body of evidence implicating reactive oxygen species (ROS), derived from many metabolic sources, in the pathogenesis of periodontal tissue destruction. ROS are generated predominantly by polymorphonuclear leukocytes (PMN) during an inflammatory response and are regarded as being highly destructive in nature. The detection of ROS oxidation products, the elevation of iron and copper ions, which catalyse the production of the most reactive radical species, and the identification of an imbalance in the oxidant/antioxidant activity within periodontal pockets, suggests a significant role for ROS in periodontal tissue destruction. In vitro studies have shown that ROS are capable of degrading a number of extracellular matrix components including proteoglycans, resulting in the modification of amino acid functional groups, leading to fragmentation of the core protein, whilst the constituent glycosaminoglycan chains undergo limited depolymerisation. The identification and characterisation of connective tissue metabolites in gingival crevicular fluid (GCF) resulting from the degradation of periodontal tissues, notably alveolar bone, provides further evidence for a role for ROS in tissue destruction associated with inflammatory periodontal diseases.

The progression of lower limb atherosclerosis is associated with IgA antibodies against Chlamydia pneumoniae

OBJECTIVE

to study the influence of serologically diagnosed chronic infection with Chlamydia pneumoniae on the progression of lower limb atherosclerosis in a group of disposed men.

MATERIAL AND METHODS

the highest systolic brachial and lowest systolic ankle blood pressures were followed for an average of 2.7 years in 129 men aged 65-73 years with conservatively treated small abdominal aortic aneurysms. Blood samples were taken to measure low-density lipoprotein and IgA and IgG titres of antibodies against C. pneumoniae by a microimmunofluorescence test.

RESULTS

the prevalences of seropositivity varied from 43 to 83% depending on the definition. The ankle-brachial blood pressure index of the IgA-seropositive [corrected] men decreases by 11%, while it decreased by 4.8% among IgA-seronegative men (p<0.05). The significant difference persisted in a multiple-regression analysis adjusting for age, smoking, initial systolic ankle BP, and initial brachial systolic or diastolic BP, but disappeared after adjusting for the level of low-density lipoprotein.

CONCLUSIONS

C. pneumoniae infection is associated with the progression of atherosclerosis.

Immunoglobulin A antibodies against Chlamydia pneumoniae are associated with expansion of abdominal aortic aneurysm

BACKGROUND

The aim of this study was to examine the possible association between the progression of small abdominal aortic aneurysm (AAA) and chronic infection with Chlamydia pneumoniae.

METHODS

Patients from a hospital-based mass screening programme for AAA with annual follow-up (mean 2.7 years) were included. After initial interview, 139 men aged 65-73 years with a small AAA underwent examination and blood sampling. Immunoglobulin (Ig) G and IgA titres against C. pneumoniae were measured by a microimmunofluorescence test.

RESULTS

Some 83 (95 per cent confidence interval 74-93) per cent of the men had an IgA titre of 20 or more, or an IgG titre of 32 or more. Men with an IgA titre of 20 or more had a 48 per cent higher AAA expansion rate than those with a titre of less than 20 (3.1 versus 2.1 mm/year; P < 0.05). Multiple linear and logistic regression analyses showed that an IgA titre of 20 or more was a significant independent predictor of increased AAA expansion, adjusted for known risk factors of expansion. Initial AAA size and serum total cholesterol level were also predictors of expansion.

CONCLUSION

A high proportion of men with a small AAA had signs of chronic infection with C. pneumoniae. Aneurysm progression correlated with evidence of chronic C. pneumoniae infection.